U.S. patent application number 12/064770 was filed with the patent office on 2008-09-25 for cellulosic molded body, method for manufacturing it and use thereof.
This patent application is currently assigned to Lenzing Aktiengesellschaft. Invention is credited to Heinrich Firgo, Gert Kroner, Harmut Ruf.
Application Number | 20080233821 12/064770 |
Document ID | / |
Family ID | 37057161 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080233821 |
Kind Code |
A1 |
Ruf; Harmut ; et
al. |
September 25, 2008 |
Cellulosic Molded Body, Method For Manufacturing It and Use
Thereof
Abstract
The present invention relates to a cellulosic molded body
containing a cellulose/clay nanocomposite, wherein the clay
component of said nanocomposite comprises a material selected from
the group consisting of unmodified hectorite clays and
hydrophilically modified hectorite clays.
Inventors: |
Ruf; Harmut; (Schorfling,
AT) ; Firgo; Heinrich; (Vocklabruck, AT) ;
Kroner; Gert; (Lenzing, AT) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
Lenzing Aktiengesellschaft
Lenzing
AT
|
Family ID: |
37057161 |
Appl. No.: |
12/064770 |
Filed: |
August 17, 2006 |
PCT Filed: |
August 17, 2006 |
PCT NO: |
PCT/AT2006/000342 |
371 Date: |
February 25, 2008 |
Current U.S.
Class: |
442/181 ;
428/221; 442/327; 501/141 |
Current CPC
Class: |
Y10T 442/60 20150401;
Y10T 428/2913 20150115; D01F 1/10 20130101; Y10T 442/30 20150401;
D01F 2/00 20130101; Y10T 428/249921 20150401 |
Class at
Publication: |
442/181 ;
501/141; 428/221; 442/327 |
International
Class: |
D01F 1/10 20060101
D01F001/10; D01F 2/00 20060101 D01F002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2005 |
AT |
A 1407/2005 |
Dec 19, 2005 |
AT |
A 2028/2005 |
Claims
1. Cellulosic moulded body containing a cellulose/clay
nanocomposite characterized in that the clay component of said
nanocomposite comprises a material selected from the group
consisting of unmodified hectorite clays and hydrophilically
modified hectorite clays.
2. Cellulosic moulded body according to claim 1, characterized in
that the portion of the clay component ranges from 5 to 40% by
weight of the moulded body.
3. Cellulosic moulded body according to claim 1 or 2, characterized
in that the moulded body has been produced from a solution of
cellulose in an aqueous tertiary amine-oxide.
4. Cellulosic moulded body according to any of the preceding
claims, characterized in that it is present in the form of a
filament fibre, a staple fibre, a film or a membrane.
5. Process for the manufacturing of a cellulosic moulded body
according to any of claims 1 to 4, comprising the subsequent steps
of a) providing cellulose b) preparing a mixture of said cellulose
with an aqueous tertiary amine-oxide c) converting said mixture
into a solution of cellulose in the aqueous tertiary amine-oxide d)
moulding said solution via a moulding tool e) precipitating said
solution in a precipitating fluid, characterized in that at least
one of steps a) to c) is carried out in the presence of a material
selected from the group consisting of unmodified hectorite clays
and hydrophilically modified hectorite clays.
6. Process according to claim 5, characterized in that in step b) a
suspension of the clay in the aqueous tertiary amine-oxide is
prepared, and that the cellulose is added to said suspension.
7. Process according to claim 6, characterized in that the clay is
dispersed in said aqueous tertiary amine-oxide by applying high
shear forces.
8. Process according to claim 6 or 7, characterized in that the
portion of the clay in said dispersion is from 1 to 4% by weight of
dispersion.
9. A textile assembly containing a cellulosic fiber according to
any of claims 1 to 4.
10. A textile assembly according to claim 9 in the form of a woven
or nonwoven article.
11. A textile assembly according to claim 9 or 10, characterized in
that the cellulosic fiber is present in a mixture with another
fiber material.
12. A textile assembly according to claim 11, characterized in that
the cellulosic fiber is present in a mixture with polyester fiber,
wherein the ratio of cellulosic fiber to polyester fiber in the
mixture is from 1:9 to 9:1, preferably 3:7 to 7:3.
13. Use of a cellulosic moulded body according to any one of claims
1 to 4 and/or a textile assembly according to any one of claims 9
to 12 as a flame-retardant article.
14. Use of a cellulosic moulded body according to any one of claims
1 to 4 and/or a textile assembly according to any one of claims 9
to 13 as a component of articles of furniture (including
upholstered sleep products such as mattresses, futons, and mattress
foundations), barrier layers in furniture (including barrier layers
between the exterior fabric and the inner stuffing of mattresses
and upholstered chaits, mattress covers, mattress pads, fiber
batting and casing material), top-of-the-bed-products (such as
sleeping pads, comforters, duvets, pillows, bedspreads, quilts and
fibre fill), panel fabric furniture, wall panels, backing for
curtains and rugs, curtains, drapes, floor coverings, tiles,
protective apparel, automotive trim surface materials, carpets,
transportation seating, textile and nonwoven products in electronic
devices (e.g. felts below keypads), bedsheets, fitted sheets,
bedcovers, bedlinen, towels, blankets in airplanes, apparel (such
as T-shirts, underwear, outerwear, trousers, shirts, socks), wall
paper, workwear, insulation material, such as for industrial
insulation, automotive insulation and housing insulation, noise
insulation materials for household devices, fabrics for decoration,
noise dampening for floorings, night wear with reduced
flammability, electrical papers, such as electrical papers for
insulations, capacitors and transformers, flock, filters, such as
air filters, oil filters and fuel filters, military uniforms and
clothing, tents, awnings, children's wear, medical drapes and
gowns, lightweight fabrics, oil rig and similar clothing, lamp
shades, and/or as reinforcement fibers, such as in plastic
materials, e.g. in polypropylene.
Description
[0001] The present invention relates to a cellulosic moulded body,
a method for manufacturing it and uses thereof.
[0002] Especially, the present invention relates to Lyocell fibres
having improved flame-retardant properties.
[0003] Lyocell fibres are cellulosic fibres produced by the
so-called "amine-oxide" or "Lyocell process". In this process, the
cellulose is dissolved directly in an aqueous tertiary amine-oxide
without the formation of a derivative, and the solution is spun.
Such fibres are also referred to as "solvent spun" fibres.
"Lyocell" is the generic name allocated by BISFA (The International
Bureau for the Standardization of Man made Fibers) for cellulose
fibres which are produced by dissolving cellulose in an organic
solvent without the formation of a derivative and extruding fibres
from said solution by means of a dry-wet spinning process or a
melt-blown process. An organic solvent is thereby understood to be
a mixture of an organic chemical and water. At present,
N-methyl-morpholine-N-oxide (NMMO) is used as an organic solvent on
a commercial scale.
[0004] In said process, the solution of the cellulose is usually
extruded by means of a forming tool, whereby it is moulded. Via an
air gap, the moulded solution enters a precipitation bath, where
the moulded body is obtained by precipitating the solution. The
moulded body is washed and optionally dried after further treatment
steps. A process for the production of Lyocell fibres is described,
for instance, in U.S. Pat. No. 4,246,221. Lyocell fibres are
distinguished by a high tensile strength, a high wet-modulus and a
high loop strength.
[0005] The Lyocell process can also be used for producing other
moulded bodies, such as films, sheets or membranes, or for
producing sponges.
[0006] There have been many attempts in the prior art to modify
cellulose moulded bodies, such as fibres, in order to impart
thereon flame-retardant properties.
[0007] As regards moulded bodies produced according to the
amine-oxide process, such as Lyocell fibres, WO 93/12173 discloses
triazine compounds containing phosphorus and their use, including
use in cellulose solutions in tertiary amine oxides.
[0008] WO 94/21724 describes flame retardants containing
phosphorus. The use thereof for Lyocell fibres is also
mentioned.
[0009] WO 94/26962 discloses a process for the manufacture of a
flame retardant Lyocell fibre. In this process, a flame retardant
is added during the manufacturing process of the fibres, before
drying of the fibres.
[0010] According to WO 96/05356, textile materials containing
Lyocell fibres are treated with compounds containing phosphorus and
nitrogen.
[0011] WO 97/02315 discloses the manufacture of a flame-retardant
Lyocell fibre, whereby a cyclic phosphine-oxide is added to the
spinning dope.
[0012] DE 44 26 966 generally mentions the addition of filling
compounds to Lyocell fibres, whereby the filling compounds are
added in high amounts.
[0013] WO 96/27638 quite generally mentions silicates as flame
retardant agents, which can be added to a Lyocell dope.
[0014] WO 04/081267 discloses modified fibres, which have been
produced according to the amine-oxide process and to which ceramic
oxides, preferably silicon dioxide, are added.
[0015] Vorbach et al., in two publications titled "Herstellung
keramischer Hohlmembranen und-filamente nach dem Lyocell-Verfahren"
in Keramische Zeitschrift 50 (3) 1998, pp. 176-179 and "Keramische
Hohlmembranen, Filamente und Strukturwerkstoff auf Basis des
Alceru-Verfahrens" in Technische Textilien (41), 1998, pp. 188-193,
mention pore forming materials which can be added to cellulosic
moulded bodies, including alumosilicates. According to the process
disclosed, cellulose only serves as a carrier polymer, which is
subsequently burned out in order to form a ceramic moulded
body.
[0016] WO 03/24890 and WO 03/24891, respectively, disclose the
addition of alumosilicates to amine-oxide-cellulose spinning dopes
for the manufacture of ceramic fibres.
[0017] WO 00/53833 discloses the use of alumosilicates in a process
for the manufacture of bicomponent fibres. Again, the purpose of
the process disclosed in this document is to produce ceramic
moulded bodies.
[0018] The above processes have several disadvantages: Some of the
known processes are expensive or use substances which are
questionable from an ecological viewpoint. Many of the processes
published up to now are not compatible with the requirements of a
continuous fibre production process. For this reason, up to now
none of the above proposals has reached the stage of production in
large scale.
[0019] Therefore, there is a desire for a flame-retardant
cellulosic moulded body, especially a fibre, which can be
manufactured in an economical way, there being no physiological or
ecological concerns regarding the flame retardant agent employed,
and where no difficulties when transferring the production process
to large-scale production are to be expected.
[0020] This object is achieved by a cellulosic moulded body
containing a cellulose/clay nanocomposite, said moulded body being
characterized in that the clay component of said nanocomposite
comprises a material selected from the group consisting of
unmodified hectorite clays and hydrophilically modified hectorite
clays.
[0021] In the moulded body of the invention, the cellulose/clay
nanocomposite is not only present on the surface of the cellulosic
body, but is also dispersed throughout the cellulosic matrix of the
moulded body. This is achieved by incorporating the hectorite clay
material in the cellulosic moulded body. The skilled artisan is
aware of the possibilities to incorporate materials into cellulosic
moulded bodies, such as adding the materials to a solution of
cellulose before moulding, or to a precursor of said solution, such
as a suspension of cellulose in a cellulose solvent.
[0022] Under "unmodified clay", a clay which has not been
chemically pretreated is to be understood.
[0023] Under "hydrophilically modified clay", a clay which has been
pretreated with agents imparting hydrophilic properties to the clay
or enforcing the existing hydrophilic properties of the clay,
respectively, is to be understood.
[0024] It is known to produce so-called "nanocomposites" of clays
and polymers, wherein the clay is intimately mixed with the polymer
matrix. In order to produce such nanocomposites, it is often
necessary to pretreat the clay material with hydrophobic organic
cations, such as alkylammonium cations. By such pretreatment, the
layers of SiO.sub.4-tetrahedrons making up the clay are exfoliated,
and the hydrophobic properties imparted on the clay layers render
the clay compatible with various polymers.
[0025] Okamoto M. provides a good overview over the technology of
Polymer/clay nanocomposites in a review in "Encyclopedia of
Nanoscience and Nanotechnology", Ed. H. S, Nalwa, Volume 8, pp
791-843, American Scientific Publishers 2004.
[0026] Nanocomposites of clays and polymers are known to have
improved flame-retardant properties, such as an increased
degradation temperature and enhanced char yields.
[0027] X. Liu et al., in a talk named "Cellulose/Clay
Nanocomposites" held at the 2nd International Conference on
Eco-Composites, 1-2 Sep. 2003, Queen Mary, University of London,
UK, describe addition of a montmorrilonite clay (Cloisite 30B of
Messr. Southern Clay), which is a clay modified with organic
cations (methyl-tallow-bis(2-hydroxyethyl)
ammoniumchloride-montmorillonite), to a cellulose solution in NMMO.
The solution is cast into a film, which is then coagulated by
dipping into water.
[0028] In several publications, ("Preparation of Cotton/Clay
Nanocomposites", Polymer Preprints 2002, Vol 43(2), 1279-1280;
"Preparation and Thermal Analysis of Cotton-Clay Nanocomposites",
J. Appl. Polym. Sci., Vol. 92, 2125-2131 (2004); "Cellulose-Based
Nanocomposites: "Fiber Production and Characterization" Polymeric
Materials: Science and Engineering 2004, Vol. 90, 40-50;
"Laboratory Scale and Nonwovens Production of Cellulose/Clay
Nanocomposites", Polymeric Materials: Science and Engineering 2004,
Vol. 91, 532-533; U.S. Pat. No. 6,893,492 B2 and WO 2005/026429
A2), White et al. describe the production of nanocomposites of
cellulose comprising up to 15% montomorillonite.
[0029] According to these publications, montmorillonite, which has
been pretreated with organic cations, is dispersed in 50% NMMO.
Cellulose material is added to this dispersion, and a solution is
produced. It is described that the solution is extruded via an
automated syringe pump to form fibres. According to these
publications, pretreatment of the montmorillonite clay with an
alkylammonium cation such as a dodecyl-ammonium salt is
mandatory.
[0030] JP-A 2002-346509 discloses shaped bodies containing
cellulose and, inter alia, montmorillonite by mixing
montmorillonite into viscose and regenerating the cellulose with
sulphuric acid. A shaped body containing 25%-75% of inorganic
fillers/clay is claimed for use as a cellulose support for garbage
disposal.
[0031] In the conference lecture "Biodegradable film nanocomposites
based on cellulose and starch" held by Golova, L. K.; Kuznetsova,
L. K.; Korolev, Yu. M.; Kulichikhin, V. G. (published in: Editor:
Bondar, V. A. Efiry Tsellyulozy i IKrakhmala: Sintez, Svoistva,
Primenenie, Materialy Yubileinoi Vserossiiskoi
Nauchno-Tekhnicheskoi Konferntsii s Mezhdunarodnym Uchastiem, 10th,
Suzdal. Russian Federation, May 5-8, 2003, 287-290 Publisher:
Izdatel'stvo "Posad", Vladimir, Russia), the mixing of
montmorillonite either in the sodium form or in the form of
hydrophobically modified montmorillonite (Cloisite 20 A, producer
Southern Clay, which is a montmorillonite modified with
dimethyl-dihydrogenated tallow quaternary ammonium chloride) to a
cellulose-NMMO-solution is disclosed.
[0032] It has now been surprisingly found that it is possible to
produce a cellulosic moulded body, such as a fiber, with improved
flame-retardant properties, by forming a cellulose/clay
nanocomposite in the moulded body, which nanocomposite comprises an
unmodified hectorite clay (i.e. a hectorite clay which has not been
chemically pretreated at all) or a hectorite clay which is
hydrophilically modified (i.e. a hectorite clay which has been
pretreated with hydrophilic agents, such as e.g. a glucosammonium
salt, contrary to treatment with hydrophobic cations such as the
alkylammonium salts mentioned above).
[0033] Especially, it has been found that hectorite, a clay of the
smectite group, not only can be successfully incorporated into a
cellulosic moulded body without any chemical pretreatment, thereby
forming a cellulose/hectorite nanocomposite, but also confers to
said moulded body improved flame-retardant properties which are
superior to those of cellulosic moulded bodies incorporating
pretreated montmorillonite clay.
[0034] In the present invention, synthetic hectorite types are
preferred over naturally occurring hectorite types.
[0035] Preferably, the portion of the clay component in the moulded
body according to the invention ranges from 5 to 40% by weight of
the moulded body.
[0036] In a further preferred embodiment, the moulded body has been
produced from a solution of cellulose in an aqueous tertiary
amine-oxide. This means, the cellulosic moulded body has been
produced by the Lyocell process. The tertiary amine-oxide
preferably is NMMO.
[0037] The moulded body may be present in the form of a filament
fibre, a staple fibre, a film or a membrane.
[0038] An especially preferred embodiment of the present invention
is a Lyocell staple fibre, containing a cellulose/clay
nanocomposite with unmodified hectorite clay as the clay
component.
[0039] Moulded bodies in the form of fibres may be further
processed to yarns, woven products such as fabrics, knits, and
nonwoven products.
[0040] A process for the manufacturing of the cellulose moulded
body of the present invention, using the Lyocell process, comprises
the subsequent steps of
a) providing cellulose b) preparing a mixture of said cellulose
with an aqueous tertiary amine-oxide c) converting said mixture
into a solution of cellulose in the aqueous tertiary amine-oxide d)
moulding said solution via a moulding tool e) precipitating said
solution in a precipitating fluid, and is characterized in that at
least one of steps a) to c) is carried out in the presence of a
material selected from the group consisting of unmodified hectorite
clays and hydrophilically modified hectorite clays.
[0041] In the process according to the invention, the clay material
may for example be added to [0042] a cellulose pulp as the starting
material of step a) [0043] during preparing the suspension of
cellulose in NMMO or to the already prepared suspension (step b) or
[0044] during dissolving the cellulose or to the solution of
cellulose in NMMO (step c).
[0045] It is well-known to the skilled artisan how to add a
material in one of steps a) to c).
[0046] A preferred embodiment of the process according to the
invention is characterized in that in step b) a first suspension of
the clay in the aqueous tertiary amine-oxide is prepared, and that
the cellulose is added to said suspension in order to form a second
suspension, which can then be further processed to a solution.
[0047] NMMO is preferably used as the aqueous tertiary
amine-oxide.
[0048] When dispersing the clay in the aqueous tertiary
amine-oxide, preferably high shear forces are applied to the clay.
This can be accomplished for example by preparing the dispersion in
an Ultra-Turrax.RTM. mixer.
[0049] The portion of the clay in said dispersion is preferably
from 1 to 4% by weight of dispersion.
[0050] An especially preferred embodiment of the process according
to the invention comprises dispersing unmodified hectorite clay in
an aqueous NMMO containing 60 to 84% by weight NMMO by means of an
Ultra-Turrax.RTM. mixer, afterwards adding the required amount of
cellulose and forming a suspension containing both the cellulose
and the hectorite clay, and forming a solution from said suspension
by methods well-known per se.
[0051] The cellulosic moulded body according to the invention,
especially when being in the form of a fibre, may be present in the
form of a blend with other types of fibres, especially inherently
flame-resistant fibres such as glass, carbon, polyphenylene
benzobisoxazole, polybenzimidazole, poly(p-phenylene
benzothiazoles), para-aramids, meta-aramids, fluorocarbons,
polyphenylene sulfides, melamines, polyimides. polyamideimides,
partially oxidized polyacrylonitrile, pre-oxidized fibres,
novoloids, chloropolymeric fibres such as those containing
polyvinyl chloride, polyvinylidene homopolymers and copolymers,
modacrylics which are vinyl chloride or vinylidene copolymer
variants of acrylonitrile fibers, fluoropolymer fibres such as
polytetrafluoroethylene or polyvinylidene fluoride, flame retardant
viscose rayons such as rayon fibres containing a phosphorus
compound, silica or alumosilicate modified silica.
[0052] Furthermore, a cellulosic fibre according to the invention
may be present in a blend with natural fibres such as cotton, flax,
hemp, kenaf, ramie, wood pulp, wool, silk, mohair or cashmere or
with man-made-fibres such as viscose rayon, polynosic rayon,
cuprammonium rayon, lyocell, cellulose esters such as cellulose
acetate, polyamides such as nylon 6, nylon 6,6, nylon 11,
polyesters such as polyethylene terephthalate, polypropylene
terephthalate, polybutylene terephthalate, polytetramethylene
terephthalate, copolyesters, polyurethane fibres, polyvinyl alcohol
fibres, polyolefins such as polypropylene or polyethylene,
polylactides, acrylics and bi-component fibres.
[0053] The fibres which are used to be blended with the cellulosic
fibre according to the invention may have been rendered flame
retardant by the application of flame retardant chemicals. Flame
retardant agents which can be utilized in accordance with
embodiments of the present invention include, but are not limited
to borates such as boric acid, zinc borate or borax, sulfamates,
phosphates such as ammonium polyphosphate, organic phosphorous
compounds, halogenated compounds such as ammonium bromide,
decabromodiphenyl oxide, or chlorinated paraffin, inorganic
hydroxides such as aluminum or magnesium hydroxide, antimony
compounds, nitrogen compounds and silica or silicates.
[0054] Furthermore, fibres which have been treated with an
intumescent compound such as melamine, pentaerythritol,
fluorocarbon, graphite, phosphated melamine, borated melamine,
sugars, and polyols, may be blended with the fibre according to the
present invention.
[0055] The fibre according to the present invention may be present
in a blend containing only one, or several of the above-listed
fibre types.
[0056] The present invention also relates to a textile assembly
containing a cellulosic fiber according to the present
invention.
[0057] The textile assembly according to the invention may be
present in the form of a woven or nonwoven article.
[0058] The nonwoven article maybe formed by way of a method
selected from the group consisting of dry-laying, air-laying and
wet-laying.
[0059] Furthermore, the nonwoven article may be bonded by way of a
method selected from the group consisting of thermal bonding,
needle-punching, hydroentanglement and chemical bonding.
[0060] In the textile assembly according to the present invention,
the cellulosic fiber may be present in a mixture with another fiber
material, as mentioned above.
[0061] In an especially preferred embodiment, the textile assembly
according to the invention is characterized in that the cellulosic
fiber is present in a mixture with polyester fiber, wherein the
ratio of cellulosic fiber to polyester fiber in the mixture is from
1:9 to 9:1, preferably 3:7 to 7:3.
[0062] It can be shown that a fibre blend containing only about 30%
of a cellulosic fibre according to the present invention and about
70% of non-modified polyester fibre, shows significantly improved
resistance to ignition and a lower rate of burning as compared with
100% polyester fibre.
[0063] The cellulosic moulded body and the textile assembly
according to the present invention have improved flame-retardant
properties, such as resistance against ignition.
[0064] Hence, the cellulosic moulded body according to the present
invention, especially in the form of a Lyocell staple fibre, and/or
the textile assembly of the present invention, are useful as
flame-retardant articles, i.e. in applications where improved
flame-retardant properties are required.
[0065] Preferable applications of the cellulosic moulded body
and/or the textile assembly according to the invention include the
use as a component of articles of furniture (including upholstered
sleep products such as mattresses, futons, and mattress
foundations), barrier layers in furniture (including barrier layers
between the exterior fabric and the inner stuffing of mattresses
and upholstered chaits, mattress covers, mattress pads, fiber
batting and casing material), top-of-the-bed-products (such as
sleeping pads, comforters, duvets, pillows, bedspreads, quilts and
fibre fill), panel fabric furniture, wall panels, backing for
curtains and rugs, curtains, drapes, floor coverings, tiles,
protective apparel, automotive trim surface materials, carpets,
transportation seating, textile and nonwoven products in electronic
devices (e.g. felts below keypads), bedsheets, fitted sheets,
bedcovers, bedlinen, towels, blankets in airplanes, apparel (such
as T-shirts, underwear, outerwear, trousers, shirts, socks), wall
paper, workwear, insulation material, such as for industrial
insulation, automotive insulation and housing insulation, noise
insulation materials for household devices, fabrics for decoration,
noise dampening for floorings, night wear with reduced
flammability, electrical papers, such as electrical papers for
insulations, capacitors and transformers, flock, filters, such as
air filters, oil filters and fuel filters, military uniforms and
clothing, tents, awnings, children's wear, medical drapes and
gowns, lightweight fabrics, oil rig and similar clothing, lamp
shades, and/or as reinforcement fibers, such as in plastic
materials, e.g. in polypropylene.
[0066] In the following, the present invention is described in more
detail by way of examples of preferred embodiments of the
invention.
EXAMPLES
Production Example 1
Discontinuous Production
[0067] Synthetic hectorite, type "Optigel SH" (Messrs. Sudchemie)
was used in this example. This is a hectorite clay which has not
been modified.
[0068] A dispersion containing 3.6% by weight of the hectorite clay
in 78% aqueous NMMO was produced in a high-shear mixer
(Ultra-Turrax.RTM. Type T50, Messrs. IKA Maschinenbau, Janke &
Kunkel, DE) by mixing the components for 1 hour at 8000 rpm.
[0069] Cellulose pulp (Type "Bahia", SCAN-viscosity 400) was added
to this dispersion in a mixer. The mixture was stirred at
80.degree. C. for one hour. After that, water was distilled off at
95.degree. C. in order to produce a spinning dope containing 13%
cellulose, 3% hectorite clay, 11% water and 76% NMMO.
[0070] The spinning dope, after having been filtered, was spun into
fibres via a jet-wet-spinning process known as such, employing a
spinneret with 247 holes of 160 .mu.m diameter each, with an output
of 0.045 g dope per spinning hole per minute, an air gap of 20 mm
length and a precipitation bath containing 25% aqueous NMMO. The
denier of the fibres was 6.7 dtex.
Production Example 2
Continuous Production at a Semi-Commercial Plant
[0071] A dispersion containing 4% unmodified hectorite clay (type
"Optigel SH") in 78% aqueous NMMO was manufactured in a similar
manner as described in example 1, using an Ultra-Turrax.RTM. high
shear mixer, Type T115KT of Messrs. IKA Maschinenbau, Janke &
Kunkel.
[0072] In a continuous process, cellulose pulp (Type "Bahia",
SCAN-viscosity 400) was added to this dispersion. The suspension
thus obtained was converted into a solution in a thin-film
treatment apparatus according to the process disclosed in EP 0 356
419 A. The resulting solution was composed of 12.0% cellulose,
2.56% Optigel SH, 11.84% water and 73.6% NMMO. The spinning dope
was filtered and spun via a jet-wet-process to fibres.
[0073] Three different types of fibres were produced, the first
type having a titre of 6.7 dtex and a cutting length of 60 mm, the
second type having a titre of 3.3 dtex and a cutting length of 51
mm, and the third type having a denier of 1.3 dtex and a cutting
length of 38 mm.
Test Methods:
[0074] To assess the flammability performance of the fibre samples,
a test method was devised in which the fibre is formed into a sheet
and exposed to a small flame.
[0075] In this test, by means of a rotor-ring-device, type "3 USTER
UDTA 3" (Messrs. Hollingworth) a card sliver is produced. In a
laboratory press, a 5 mm short cut is produced. 7 g of this short
cut are dispersed by means of a laboratory desintegrator according
to ISO 5263 in 2 L of water, employing 3000 rotations of the
stirrer. The fibre suspension is filled into the cylinder of a
sheet forming apparatus of the "Rapid-Ko then" type according to
ISO 5269/2 and DIN 54358, respectively (manufactured by Messrs.
Paper Testing Instruments GmbH) and, according to an automated
program, a sheet of 200 g/m.sup.2 is produced. The sheet is dried
at 92.degree. C. for 20 minutes and conditioned.
[0076] In order to carry out a test for flame resistance, this
cellulose sheet is fixed in a vertically arranged round steel frame
with an inner diameter of 150 mm. A small gas flame (vertical size
4 cm, gas consisting of 3.4% propane, 49.4% butane, 17% acetone,
1.5% methyl-acetylene, 27.7% propene and 1% propadiene) is moved
horizontally towards the sheet, whereby the vertical distance to
the lower inner edge of the steel frame is 2 cm and the horizontal
distance to the sheet is 1 cm.
[0077] The action of the flame is maintained for 5 minutes. The
behaviour of the sheet towards the action of the flame is observed
(i.e. whether the flame breaks through the sheet or the material is
only partly or fully charred and forms a barrier). If the sheet is
charred, the size of the charred area and its robustness (i.e.
whether the sheet is destroyed upon touching or maintains a certain
amount of residual tenacity) are observed. A larger charred area
means that the sheet has suffered greater damage due to the
sustained combustion. A charred area which is fragile and easily
broken when touched would offer less protection to underlying
materials.
[0078] In the following tables, Lyocell staple fibres according to
the invention and produced according to examples 1 and 2,
respectively, were compared with [0079] standard Lyocell staple
fibres (containing no modifying agent), [0080] Lyocell staple
fibres containing other materials, such as kaolin, talkum, and two
different hydrophobically modified montmorillonite clays, and
[0081] a commercially available flame-retardant viscose fibre (Type
"VISCOSE FR").
[0082] The materials underlying Test Examples 1 to 6 of the table
were produced by applying the conditions set out in Production
Example 1.
[0083] The materials underlying Test Examples 9 to 11 of the table
were produced by applying the conditions set out in Production
Example 2.
TABLE-US-00001 TABLE Amount of additive (% Flame Denier of by
weight break Portion of Robustness Test Fibre Manu- Type of fibre
of through charred of charred Example Type Additive facturer
additive (dtex) cellulose) time (s)* area (%) area 1 Lyocell
Laponite Rock- Unmodified 6.7 23.0 >300 30.3 flexible, is RD
wood Hectorite not Additives destroyed upon touching 2 Lyocell
Optigel Sud- Unmodified 6.7 23.0 >300 38.4 flexible, is SH
chemie Hectorite not destroyed upon touching 3 (C) Lyocell Ultra-
Engel- Kaolin 6.7 23.0 >300 71.8 is destroyed gloss 90 hard upon
touching 4 (C) Lyocell Talkum Naintsch Talkum 6.7 23.0 ~60 70.8 is
destroyed A 7 upon touching 5 (C) Lyocell Nanofil - Sud- Mont- 6.7
23.0 >300 76.9 flexible, is 9 chemie morillonite, not modified
destroyed with upon benzylmethyl touching distearyl- ammonium salt
6 (C) Lyocell Nanofil - Sud- Mont- 6.7 23.0 >300 100 destroyed 8
chemie morillonite, modified with dimethyldi- stearyl- ammonium
salt 7 (C) Lenzing 5.5 ~70 33 Minor Viskos damage FR .RTM. 8 (C)
Lyocell none - -- 6.7 burns com- pletely 9 Lyocell Optigel Sud-
Unmodified 6.7 21.3 >300 31.3 flexible, is SH chemie Hectorite
not destroyed upon touching 10 Lyocell Optigel Sud- Unmodified 3.3
21.3 >300 45.5 flexible, is SH chemie Hectorite not destroyed
upon touching 11 Lyocell Optigel Sud- Unmodified 1.3 21.3 ~70 47.2
flexible, is SH chemie Hectorite not destroyed upon touching *A
flame break-through time of >300 s means that the test was
stopped after 300 s without the flame having broken through the
cellulose sheet.
[0084] As apparent from the above table, the Lyocell fibres
according to the present invention are clearly superior to the
other Lyocell fibres according to the comparison examples (marked
with (C)) and comparable to the well-established commercially
available Lenzing Viscose FR.RTM.-fibre. Especially, if compared
with the Lyocell fibres containing modified montmorillonite, it can
be seen that the portion of charred area of the
montmorillonite-containing fibres is much higher than that of the
fibres according to the invention.
[0085] FIGS. 1 and 2, respectively, show the results of the
above-described test with a fiber sheet made of 33% Lyocell fiber
containing Optigel.RTM.g SH hectorite clay and 67% polyester fiber
(FIG. 1) and a fiber sheet made of 100% polyester fiber.
[0086] It is clearly apparent from the figures, that the mixture of
the fiber according to the invention and polyester fiber is only
partly charred (cf. the black area in FIG. 1), whereas a sheet made
from 100% polyester fiber is completely burned down.
[0087] This means that even if the fiber according to the invention
is admixed in only small portions to other fiber types, excellent
resistance against the action of a flame can be achieved.
[0088] The response to flame contact of the fibre according to
example 9 of the above table was, furthermore, determined
additionally according to DIN 54 336 (Vertical method, edge
ignition).
[0089] The fibre was tested in the form of a lightly needled
nonwoven:
TABLE-US-00002 Length of Velocity of destroyed flame Area Weight
area spreading (g/m.sup.2) (mm) (mm/s) Remarks 50 430 53 100 430 10
200 30 -- Flame extinguishes after 13 s
* * * * *